Heat exchange fin



June 18, 1946. c. A. sEwELL 2,402,262

HEAT EXCHANGE FIN Filed ug. 30, 1945 2 Sheets-Sheet l @4. JMW

CLEVELAND A. SEI/VEL L June 18, 1946. c. A. sEwELL HEAT EXCHANGE FINFiled Aug. 30, 1943 2 Sheets-Sheet 2 31u/ummm ci. EvEmA/DASEWHLLPatented June 18, 1945 HEAT EXCHANGE FIN Cleveland A. Sewell, Newark, N.J., assgnor to American Coils Co., Newark, N. J., a firm consisting ofBessie Binder, Thomas Binder, and

Harold Binder Application August ao, '1943. seriaiNo. 500,567

This invention is directed to a methodof fabri eating and theconstruction of heat-exchange fins, with the particular purpose ofincreasing the heat-exchange function, avoiding the possibility of iininsulation by retarded air flowI and provide for a perfect mechanicalbond between the iin and the carrying tube.

In heat exchange constructions involving the provision of 'a carryingtube and a plurality of heat-exchange fins secured thereon, it has beenfound that the conventional arrangement is more or less ineiilcient fordesired heat exchange, in that it usually provides a flat surface withparallel air iiow, causing a small film of air in immediate contact withthe n to act as an insulating layer for the iin and materially retardthe effective heat exchange, and necessitating the increase of finsurface or the quantity of air passing over the fins for proper results.

` An essential object of the present invention is therefore to so formthe iin area. as to, in effeet, materially increase the iin area withwhich the air contacts to thereby expose a relatively greater finsurface to the flow of air per lineal feet of iin surface, to therebyavoid insulating air film and permit effective heat exchange with s airunder lower volume andpressure.

" Again many fins have been designed to create turbulence in the airstream to break up interfering and insulatingair films, but suchconstructions have, for effective heat exchange, been formed to retardthe air flow and require higher air-flow pressure or greater volume ofair.

It is a further object of the present invention to form the iin with aview to creating the necessary turbulence without material retarding ofair flow to thereby permit.active clearance of air past the iin in amannery to insure, maximum heat exchange.

The conventional heat-exchange units involve the use of a tube andheat-exchange fins secured to the tube normal to its axis, with the finshaving integral spacer strips which overlie and bear on the tube andlimit the positions of the adjacent fins. The conventionally formedspacer strips have their roots in the margin of the tube receivingopening in the fin, and in this particular provide a. decided objectionto the use of a mechanical bond between the fin and tube, espe.l

cially where such mechanical bond involves the expanding of the tube toembed the edge of the iin opening.

A'further, and particularly important feature of the present inventionis the provision of the desired spacer strips for the n with such strips4 Claims. (Cl. 257-262) integral with and extending from the fin, but

with the strips so connected to the iin that the edge margin of the tubeopening in the fin is completely free of any strip connection, to permitsuch edge margin of the tube opening to retain throughout itscircumferential length its normal relatively sharp edge for-convenientlyembedding the tube under expansion of the latter, for certainty andrigidity of fin mounting form Fig. 6 is a front elevation of a slightlymodifiedY type of fin construction.

Fig. 7 is a perspective view of the modified type of fin shown in Fig.6.

Figure 8 is a view partly in elevation and partly in section of themodification shown in Figures 6 and 7.

Fig. 9 is an elevational view of a fin constructed in accordance withanother embodiment of the invention, and

Fig. 10 is a sectional View taken substantially on the line' lll- IIJ ofFig. 9, a second position of the spacer strips being indicated by brokenlines? The method of construction resides in slitting the outer edge ofthe iin body on radial lines extending a predetermined distance towardbut not meeting the usual tube receiving opening formed centrally of theiin, and then deiiecting the independent vanes so formed from the normalpiane of the fin body to provide increased heatexchange surface; themethod also involvingthe provision of 1in-spacer strips integral withthe fin, but with their roots projecting from the iin body 'at pointsoutwardly of the margin of the tube tube opening, the n-vanes being thenrelatively distorted or deected with respect to the normal n plane; theiin body being then cut out at desired spaced intervals to providespacer strips,v

the spacer strips being so cut from the body as to have their rootportions extending from the body at points adjacent but wholly beyondthe margin of the tube opening in the iin, for the purpose of leavingsuch margin completely uninterrupted for mechanical bonding of the finand tube.

With a view to a better understanding of the method the mechanicalconstruction of the iin will be explained in the light of the drawings.

In the form shown yin Figs. l to inclusive, the fin body I is shown asrectangular in form, centrally formed with an opening 2 to receive theconventional tube 3. 'I'he tube is of a character to permit a mechanicalbond between the tube and n by appropriately expanding the tube afterapplication of the ns to cause the edge of the opening 2 to embed itselfin the material of the tube, and obviously to provide a proper thermalcontact and effective securing of the n in place, the full,uninterrupted margin of the tube opening 2 must be so embedded.

The outer edge of the fin body is slitted on radial lines 4, openingthrough the outer edge and extending toward the tube opening 2, butterminating materially short thereof to leave a flat area 5 in thenormal plane of the fin between the tube opening 2 and the ends of theradial slits 4. The slits provide n-vanes 6, each connected with the finbody but each independent of the other beyond the area 5 of the body.

The fin-vanes are in the form-being described twisted on theirlongitudinal axes, as'at 7, to present one half of each vane onopposites of the normal plane of the body. The vanes 6 are so twisted asto present parallel air contact areas deilnitely spaced one from theother and each at a slight angle to the normal plane of the n relativeto the tube. 'I'he material -of the flat area 5 of the iin is utilizedto form the spacer-strips indicated at 8, which strips are cut from thefiat area 5 so as to leave the connected portion o'r root of the stripat a point 9, which as clearly shown in Fig. 4 is outwardly of andwholly free of the margin of the tube opening 2. The strips 8 are thenbent from their roots into a position to extend at substantially rightangles to the iin to overlie and bear on the tube 3 when the iin isapplied. This particular construction of the spacer strips, of whichthere may be any desired number, avoids any interference with the sharpedge of the margin of opening 2 and at the same time leaves a smallmargin of n body, as at IB'to provide an abutting area for the ends ofthe strips of adjacent iins for spacing purposes. It is of courseunderstood that the spacer strips are of such lengths as to provide theusual spacing function relative to adjacent iins in the application ofthe ns.

In the form of the invention shown more particularly in Figs. 6, 7, and8, the construction of the fin is identical with that previouslydescribed, and the same reference numerals are used in these gures toidentify the same parts previously described. This modled form, however,diilers from the preferred form in that the n-vanes, shown in themodilled form at II, are not twisted in angular relation to the normalplane of the fin, but are bodily deected at the roots in successivelyopposite directions from the normal plane of the fin and then extendedin planes radial oi "but slightly offset from the normal plane of thebody. In this form, viewing the lin ln edge relation, the vanes I I aresuccessively oppositely positioned and define an uninterrupted spacebetween them for air ow, with the marginal edges fully open to aircontact.

In this modified form the spacer strips 8 are formed as previouslydescribed, and in effect the modied form differs from the preferred formonly in the relation of the iin-vanesto the normal plane of the 1inbody.

From the constructions described it will be seen that the amount each nnvane is deflected olf the center of the plane of the 1in is equal tovone-half the iin spacing of the iinal surface, and in setting the finson the tube care must be taken that the alternate iins be the full iinspacing, so that vanes of adjacent fins when on the tube shall projecton the similar sides of the iin planes to maintain this spacing.

The iin vanes act as individual n sections, but as they act alternatelyand oppositely on the air stream, the air is permitted to flow throughWithout undue obstruction, and yet no part of the air stream ispermitted to form an air lm adjacent the fln surface. By this formationapproximately fifty per cent more of the iin surface is subject to theair stream than is possible by a flat iin. Thel improved n is moreelective as a heat-exchange unit because more fln area is exposed to theair stream per lineal feet of surface; the exposed edges of the vanesprovide additional exchange surface, being effective in theirobstructive function; and as there is no air nlm on the surfaceeffective heat exchange may be accomplished with a lower pressure dropin the ow of the air.

In the particular construction of the spacer strips, it will be apparentthat if the strip had its root directly at the margin of the tubeopening Ci, such root would present an obstruction to the free embeddingof the margin in the tube in the mechanical bonding. Thus effectivebonding would be diiilcult preventing not only proper contact of thetube and-fin, but proper xing of the iin in place. By the .improvedspacer-strip formation the margin of the tube opening 2 is completelyunobstructed presenting a uniform edge which, under expansion of thetube under anyusualr or preferred method, may be evenly and correctlyembedded into the material of the tube to insure a proper holding of theiin and also a proper metallic contact between the tube and n.

In the embodiment of the invention as illustrated in Figures 9 and 10,the iin body I2 is initially produced with the spacer strips I4extending inwardly and radially of the central opening I5. However, asthe body I2 is placed upon the tube I6, the spacer strips I4 exoutwardly, as indicated by broken lines in Figure 10. It is believed tobe obvious that these strips I4 are of such length to provide therequired spacing between adjacent bodies. It is believed to be obviousthat the body as illustrated in Figures 9 and 10 can be initiallystamped and in a manner wherebythere is but a minimum of waste material.

While the present invention is more particularly designed for use incooling air, it is to be understood that the improved iin is equallyeffective in other heat-exchange requirements, and that any and all suchadditional uses are contemplated as within the spirit of the presentinvention.

Having thus described the invention, what is `claimed as new, is:

1. A heat-exchange iin comprising, a central annular fin body having anopening therethrough u assembly formed by an even number of radial'vanes each attached at one end to-said body and projecting radially fromsaid body, said vanes being offset axially with respect to said centralbody with the vanes being in two groups offset in opposite directionsand with the vanes in the two groups alternately positioned whereby eachvane is oiiset in the opposite direction from the two next adjacentvanes, said body being substantially in a single plane and with thevanes of the two groups being substantially in single planesrespectively n Opposite sides of the plane of said body.

2. A heat-exchange iin as described in claim 1, wherein the o'utercontour of the lin is substantially rectangular and wherein the vanesare separated by radial slits which extend inwardly from the nperiphery.

3. A rectangular heat-exchange fin comprising, a central fin body havingan opening therethrough defined by a substantially uninterrupted innermargin which is adapted to receive snugly an expansible metal tube, anda heat-exchange vane assembly formed by an even number of peripherallypositioned vanes each attached at one end to ,said central n body andprojecting from said central n body, said vanes being separated by slitswhich extend inwardly from the periphery of the fin to said central bodyand with the vanes ybeing offset with respect to said central body andbeing in two groups which are offset in opposite directions with thevanes in the two groups alternately positioned whereby each two adjacenttins are offset in the opposite directions, said central n body beingsubstantially in a single plane and said tins of the two groups beingrespectively in -two parallel planes which are olfset with respect toeach other and also on opposite sides of and offset with respect to theplane of said central body.

' 4. A heat-exchange fin as described in claim 3 which includes aplurality of integral spacing members which are attached to said centraliln body at points spaced fromsaid central body and which project fromsaid central body and act as spacer members and heat-exchange 1inportions.

CLEVELAND A. SEWELL.

